A slide fastener typically is formed by a pair of longitudinally extending and parallel textile tapes having confronting edges that carry interleavable coupling elements. These elements, which are typically made of a synthetic-resin coiled or meandered monofilament, do not extend the full length of the respective tapes and are joined together at their one ends by a so-called bottom end stop and each carry at their opposite ends a so-called top stop. A slide can move along both elements and is constructed such that on longitudinal movement from the bottom stop toward the top stops it interleaves, that is joins, the two coupling elements, and on opposite movement it separates them.
Such fasteners are typically made in a mass production operation in five different steps starting from a basic workpiece comprised of two very long parallel tapes whose confronting edges carry full-length coupling elements that are usually joined together In a first machine a gap is formed in the joined coupling elements, same being cut away or otherwise removed for short distances at locations spaced along the tapes by the length of the fasteners to be made. Then the bottom end stops are fitted to the joined coupling elements at what is normally relative to the direction of travel of the tapes the trailing edges of each gap. A slider is then fitted to the elements from the leading edge of each gap, being slid on in a direction tending to separate the elements. Subsequently the top stops are applied to the separated coupling elements immediately downstream of the slider at the leading end of each gap. Finally the tapes are cut transversely across generally through the center of the gap, separating out the individual fasteners.
These various machines, which may be supplemented by packing machines and the like, typically operate at widely different speeds. Some of the machines, for instance the gapper, inherently can only process a certain number of fasteners in a given amount of time while others can operate much more rapidly. In a standard setup two gapping machines feed a single machine for installing bottom stops, and same in turn feeds its output to several slider-installing units.
Thus the known fastener-manufacturing systems must have duplicates of some of the processing machines, so that when zipper size and/or style changes several machines doing the same process must be reprogrammed or adjusted. In general any change in the run requires that the production line be shut down a considerable amount of time.
In German patent document No. 3,172,401 filed Apr. 11, 1987 a solution to this problem was proposed in the form of a system which has only one machine for each step of the manufacture, and where the workpiece is fed serially through the succeeding machines. In order to compensate for the slowest machine, which in the case of this system is a welding machine at the upstream end of the line, storage units or buffers are provided between succeeding machines. In addition a counter is provided for each of the machines except the extreme downstream machine as well as a system to monitor how much of the workpiece is in the upstream buffer. Thus when an upstream machine has operated a predetermined number of cycles and has fed into the buffer hopper immediately downstream of itself a corresponding number of partially finished fasteners, the downstream machine is started and operates until the buffer is empty, whereupon it stops and waits until the immediately upstream machine has one again cycled the predetermined number of times.
Such an arrangement, while being some improvement on the system with parallel machines compensating for a slow machine, still is relatively unwieldy, and can only operate when the slowest of the machines is at the upstream end of the line. In addition this system is not easy to switch over from one size and/or style of fastener to another in that it requires that each and every machine be separately reset.